3^(@)" If "^(n)C_(r-1)=^(n)C_(3r)" then "r" is "

If .^(n)C_(r-1)=.^(n)C_(3r) , find r.

If ""^(n)P_(r)=""^(n)P_((r+1)) and ""^(n)C_(r) = ""^(n)C_(r-1), then (n,r) =

If ""^(n)C_(r-1):""^(n)C_(r):""^(n)C_(r+1)=2:4:5 then (n,r) is

" If "^(n+1)C_(r+1):^(n)C_(r):^(n-1)C_(r-1)=11:6:3," then "nr=

If ""^(n) C_(r-1) = 36 and ""^(n) C_(r ) = 84 , then a) 13r-3n-3=0 b) 10r-3n-3=0 c) 10r+ 3n-3=0 d) 10r-3n+ 3=0